A control system for a semiconductor device is required to achieve a high precision, a high functionality, and a high packaging density at a low cost. In the control system, an improvement in the precision of various sensing functions is one of important problems to be solved to achieve an improvement in the efficiency of the semiconductor device. One of impediments to the achievement of an improvement in precision is a variation in performance due to temperature characteristics of electronic components. Accordingly, it is necessary to take some measures to reduce the variation in performance.
Note that a photocoupler is an electronic component that is generally used to transmit signals from a logic part and a semiconductor device, while providing electrical isolation between the logic part and the semiconductor device. A technique in which a light emitting diode of a photocoupler detects abnormal heat generation in the photocoupler has been proposed (e.g., see PTL 1).